Some aqueous inkjet inks are formulated with large metal oxide pigment particles; i.e., particles that have an effective particle size that is larger than 100 nm. Examples of such inks include TiO2 pigment-based inks and ceramic pigment-based inks. In some instances, the large metal oxide pigment particles settle out of the aqueous medium of the ink during a period of nonuse, and the particles agglomerate in the sediment. It has been found that the agglomeration of settled pigment particles affects the long term usability of the inkjet ink. For instance, the agglomerated particles may compromise the jetting reliability of an inkjet pen, e.g., agglomerated particles may clog the nozzles of the inkjet pen during printing.